Heating and cooling system



Oct. 18, 1966 L. H. LEONARD, JR 3,278,978

HEATING AND COOLING SYSTEM Filed June 25, 1964 IN V EN TOR.

ATTORNEY- LOUIS H. LEONARD, JR.

United States Patent 3,278,978 HEATING AND COOLING SYSTEM Louis H.Leonard, Jr., Dewitt, N.Y., assignor to Carrier Corporation, Syracuse,N.Y., a corporation of Delaware Filed June 23, 1964, Ser. No. 377,315 4Claims. (Cl. 165-62) This invention relates broadly to a heating andcooling system. More particularly, this invention relates to a heatingand cooling system employing a'refrigeration apparatus. Still moreparticularly, this invention relates to a system of the kind describedwherein improved refrigerant handling means are provided.

My copending patent application, Serial No. 377,319, for a Heating andCooling System, filed on the same date as the present patentapplication, discloses a system for heating and cooling wherein a steamcondenser is purged of noncondensible vapor, such as refrigerant vapor,to control operation of the system and to provide eflicient heating of aload to be heated. The refrigerant vapor is removed from the steamcondenser by means of a purge operated by a Water driven jet pump. Inorder to assure optimum operation of the purge system, the temperatureof the jet impelling water should be low enough to prevent the purge jetwater from flashing in the jet at the venturi.

During winter heating operation, when cooling is not required, it may bedesirable to withdraw the refrigerant from the normal refrigerantcircuit, for example, in order to reduce the load on the purge system.It is also sometimes necessary to withdraw the refrigerant in order toservice the machine. In order to facilitate shipping the machinepre-charged with refrigerant, thus reducing the overall cost of theequipment when it is installed and ready to operate, some means shouldbe provided to hold the refrigerant out of the refrigerant circuit, asis understood in the art. While the refrigerant may be kept in a tankseparate from the machine, contamination of the refrigerant may resultand additional time and equipment are necessary, in transferring therefrigerant between the machine and a separate container. Furthermore,the use of a refrigerant container separate from the machine does notfacilitate factory charging of the machine.

It is a primary object of this invention to provide a new and improvedheating and cooling system and a method for handling and storingrefrigerant in a refrigeration system.

Another object is to provide a new and improved method of passingrefrigerant vapor from a cooler to a refrigerant storage vessel uponstopping normal cooling operation of the system, and providing atemperature in the vessel below the saturation temperature correspondingto the vapor pressure of the refrigerant, thereby condensing andretaining the refrigerant in the vessel. A related object is provisionfor passing the refrigerant from the vessel to the cooler upon startingthe system in normal cooling operation.

Still another object is provision of a new and improved heating andcooling system including a cooler having a water sump, a steam condenserfor condensing steam and heating a heating medium for circulation to aload to be heated, with steam driven operating means for dischargingsteam into the steam condenser and for circulating refrigerant throughthe cooler during cooling operation of the system, a purge systemoperable upon circulating impeller water from the sump at a temperaturebelow that in the steam condenser for removing noncondensibles from thesteam condenser and discharging the water and noncondensibles into thesump, a storage vessel connected with the cooler for the passage ofrefrigerant from the Patented Oct. 18, 1966 "ice cooler into the vesselwhen the operating means is inoperative and for the passage ofrefrigerant from the vessel intothe cooler when the operating means isin operation, a bypass around the operating means for passing steam intothe steam condenser to heat the heating medium and to render theoperating means inoperative during winter heating operation of thesystem, and a heat exchanger in circuit during winter heating operationto associate the impeller water and the heating medium returning to thesteam condenser to provide an impeller water temperature below that inthe steam condenser, thereby efrectively preventing flashing of thewater in the purge system.

Another object is provision of a new and improved cooling systemincluding a refrigerant circuit, storage means for withdrawingrefrigerant from the circuit when the system is inoperative for cooling,and operating means operable for circulating refrigerant through thecircuit during cooling operation of the system and providing a pressurein the circuit below that in the storage means for withdrawing therefrigerant from the storage means.

Another object is provision of a new and improved heating systemincluding enclosing means for a heated vapor, the enclosing meansreceiving a heating medium passing to a load to be heated, a purgesystem including a jet pump for removing noncondensibles from the steamcondenser responsive to circulating impeller water to the jet pump, anda heat exchanger to associate the impeller water and the heating mediumreturning to the enclosing means to provide an impeller watertemperature below that of water in the enclosing means, therebyeffectively preventing flashing of the purged water in the purge system.

The drawing is a flow diagram of a preferred embodiment of the inventionin a heating and cooling system.

The invention is illustrated in the form of a heating and cooling systemfor providing cooling, heating, or simultaneous heating and cooling. Thesystem is preferably hermetic in that fluids in the system areeffectively prevented from escaping and ambient air is kept out of thesystem. The system may be considered as having a power side including acircuit for the circulation of a power fluid, a refrigerant sideincluding a circuit for the flow of a refrigerant fluid under theinfluence of operating means driven by the power fluid, with theoperation of the system regulated by a control system.

The invention will be described with reference to a preferred powerfluid, which is water, and a preferred refrigerant, which isoctafluorocyclobutane, commonly referred to as C318 and having achemical formula C F These fluids are particularly preferred because oftheir relative immiscibility and because they are inherently highlystable and do not tend to decompose or chemically react with each otheror other materials in the system, or cause or promote corrosion orundesirable by-products. Also, this refrigerant is a relativelynoncondensible vapor at the temperatures and pressures at which thepower fluid (water) condenses, as well as at the usual ambientatmospheric conditions of temperature and pressure. However, other powerfluids and refrigerants having these desired chemical and physicalproperties may be utilized within the scope of this invention.

As illustrated in the drawing, the power side includes a suitable steamgenerator 12 having a burner 13 connected with a mixing chamber 14 formixing a fuel, such as gas, received through a gas line 15 having amodulating flow regulating gas valve 16, and air received through acombustion air line 17 from a blower 18. The steam generator 12 suppliessteam at a substantially constant pressure (15 p.s.i.g., for example) ascontrolled by a constant pressure regulating valve 19 in a steam supplyline 20 to operating means in the form of a turbocompressor 21, and moreparticularly, a turbine 22 which discharges steam through a dischargeline 23 to a steam condenser 24. A steam condensate pump 25 returns thesteam condensate through areturn line 26 from the steam condenser 24 tothe steam generator 12 for recirculation through the power side of thesystem. The tubocornpressor 21 has flow restricting means in the form ofseals, as 27, for retarding leakage of steam and refrigerant from theturbine 22 and the compressor 32, respectively, and water lubricatedbearings, as 27", and the steam condensate pump 25 pumps steamcondensate through a lubricant water line 28 including a lubricantcooling heat exchanger '29 for lubricating the bearings 27". Leakagefrom the turbine and compressor, and water from the bearings 27", passinto a chamber 30 and through a drain line 31 to the steam condenser 24.

The refrigerant side of the system includes a refrigerant compressor 32of the turbocompressor 21. The compressor 32 is drivingly connected withthe turbine 22 for passing compressed refrigerant vapor to a refrigerantcondenser 33. Condensed refrigerant passes from the refrigerantcondenser 33 to a refrigerant subcooler 34 and through a suitablerefrigerant flow restricting means 35 into a evaporator or cooler 36,from which the refrigerant vapor is withdrawn by the refrigerantcompressor through a suction line 37, thus completing the refrigerantcircuit of the system. The cooler includes a water supply sump 38 andprovides means for separating Water and refrigerant. A chilled Waterline 39 communicates with a tube bundle 40 in the cooler 36 for carryinga heat exchange medium, here in the form of chilled water, which iscooled by the refrigerant and circulated by a chilled water pump 41 toan area having a cooling requirement. The cooling capacity of the systemvaries in proportion to the compressor speed.

A cooling tower or condensing water pump 42 circulates tower waterthrough an inlet line 43 to the refrigerant subcooler 34 and into therefrigerant condenser 33 and then the steam condenser 24 and back to thetower through an outlet line 44. A branch line 45 in the condensingwater inlet line 43 provides tower water to the lubricant water heatexchanger 29 for cooling the lubricant water, and this branch terminatesin the return line 44 to the tower. In general, control of condensingwater temperature and flow rate is unnecessary, thus minimizing scalingof condensing surfaces in the condensers.

The control system regulates the cooling and simultaneous cooling andheating'capacities of the refrigeration system by varying the steamcondenser pressure which is related to the condensing rate of steamdischarged into the steam condenser 24. The condensing rate of the steamcondenser is regulated by controlled blanketing of a first condensingportion or tube bundle 46 with a noncondensible vapor, hereinrefrigerant vapor, introduced through a refrigerant line 47 from thecooler 36.

The quantity of noncondensible vapor effectively blanketing the firstcondensing portion 46 of the steam condenser is regulated by amodulating refrigerant flow regulating valve 48 in the line 47. Thevalve 48 is actuated responsive to leaving chilled water temperature bymeans of a temperature sensor 49 on a leaving branch of the chilledwater line 39. For example, as the cooling load drops, more refrigerantis introduced into the steam condenser 24, thus reducing the steamcondensing rate to increase the steam condenser pressure and thereforethe temperature of the saturated steam in the condenser, and the turbineback pressure to reduce the turbocompressor power output and in general,the turbocompressor speed.

A purge system withdraws refrigerant from the steam condenser 24,preferably at a constant rate. Herein a constant speed water supply pump50 in a water line 51 recirculates impellerwater from the cooler sump 38for operating a jet pump 52 in the sump to withdraw noncondensible vaporfrom the steam condenser 24 through a purge line 53 opening into thethroat of the jet pump 52. The water supply pump 50 further providesmakeup water for the steam generator 12 through a make-up water line 54to the steam condenser 24.

Simultaneous heating and cooling, wherein the heating and coolingcapacities of the system vary inversely of each other, is provided. Asecond condensing portion or'tube bundle 55 in the steam condenser 24 ismaintained etfectively free of blanketing by refrigerant vapor tomaintain its full condensing capacity and maximum heating of a heatingmedium, herein water, circulated through the bundle 55 and to a load tobe heated by means .of a heating water pump 56 in a heating line 57including a leaving branch 58to the area having a heating requirementand a returning branch 59 back to the second con densing portion 55.

The refrigerant injected into the steam condenser to blanket the firstcondensing portion 46 enters the steam condenser through a refrigerantport 60 at the end of the refrigerant line 47 within one end of thesteam condenser 24 between the first condensing tube bundle 46 and thesecond condensing tube bundle 55 adjacent an end of the bundles. Abafile 61 extends between upper and lower portions of the steamcondenser between the first and second condensing tube bundle 46 and 55,to prevent the flow of fluids therebetween except in a limited area ofcommunication 62 at the refrigerant port 60. The entering steam firstflows from the discharge line 23 through a steam condenser inlet port 63at an end of the condenser. 24 opposite the area of limitedcommunication 62,1and across the second condensing tube bundle 55, thenthrough the area of limited communication 62 and past the refrigerantinlet port 60, and then past the first condensing bundle 46. Therefrigerant vapor. entering the steam condenser 24 is drawn across thetubes of the first condensing bundle 46, and in the illustratedembodiment each tube is effectively individually enveloped by a sheathor layer or refrigerant vapor thereby insulating the tubes of the firstcondensing bundle from the steam to reduce the steam condensingcapacity. A condensate chamber 64 of the steam condenser 24 is incommunication with the interior of a body shell 65 of the steamcondenser through a port.

66 at the bottom of the condenser and at the same end of the condenseras the steam inlet port 63. The drain line 31, the make-up Water line 54and the condensate return line 26 open into the chamber 64. Thus, theturbocompressor chamber 30, the steam discharge passage 23, the drain31, and the steam condenser 24 are all at substan; tially the samepressure, that is, the steam condenser pressure which is normally belowambient atmospheric pres,- sure during normal cooling operation.

The purge line 53 opens into the steam condensate chamber 64 at a levelto withdraw steamcondensate from the chamber should the condensate levelrise too high. Responsive to a low condensate level in the condensatechamber, a float actuated sensor 67 in the chamber opens a normallyclosed shutofi valve 68 in the make-up water line 54 from the watersupply pump 50, to maintain a minimum level of condensate in the chamber64.

At high cooling capacity, only a small quantity of refrigerant is in thesteam condenser 24 to blanket the first condensing portion 46 so thatthe steam condenser pres-. sure is low and the temperature of saturatedsteam in the condenser is correspondingly low. Therefore, the temperature of the water in the second condensing portion 55 j is low andlittle heat is provided for the load to be heated. Conversely, when thecooling capacity is low the heating capacity is normally high.-

In the illustrated embodiment, a shell 77 of the refrigerant condenser33 envelopes the steam condenser.

shell 65 so that refrigerant, which is normally above atmosphericpressure in the refrigerant condenser 33, cf-

fectively prevents the entry of ambient air into the steamy condenser 24and insulates the steam condenser during winter heating operation tofacilitate maximum heating of the second tube bundle 55. A condensingtube bundle 78 Q in the refrigerant condenser 33 receives tower waterfrom the refrigerant subcooler 34 and passes the water to the steamcondenser first condensing bundle 46.

Responsive to the turbine 22 driving the compressor 32, refrigerantvapor is compressed and passes through a compressor discharge line 79and into the refrigerant condenser 33 where it is condensed and cooled.The refrigerant condensate flows through a refrigerant condensate line80 into the refrigerant subcooler 34 from which it passes through therefrigerant flow restricting means 35, here in the form of a float valveunit, and flows through a cooler refrigerant supply line 81 and into acooler refrigerant inlet 82 extending through a shell 83 of the cooler36. A suitable equalizer line 84 connects the float valve unit chamberand the refrigerant condenser, for reasons well understood in the art.

The refrigerant inlet 82 opens into a pan 85 spaced above the bottom ofthe cooler shell 83 which defines the sump 38. The chiller water bundle40 is in the pan 85 so that during normal cooling operation of thesystem, the bundle is flooded by boiling refrigerant. As the refrigerantvaporizes, it passes into a refrigerant chamber 86 in an upper portionof the cooler shell 83 above the pan 85. The refrigerant suction line 37to the compressor 32 opens into an upper portion of the refrigerantchamber 86.

During cooling operation of the system, water in the sump 38 ismaintained at least F. above the temperaature in the refrigerant chamber86, so that refrigerant in the sump is a vapor, as is more fullydescribed in my copending United States patent applicant, Serial No.377,258, for a Heating and Cooling System, and filed on the same date asthe present application. Refrigerant vapor in the sump passes upwardlyabout a left end wall 87 of the refrigerant pan 85 and into therefrigerant chamber 86 from which it is withdrawn through the suctionline 37. Any Water in the refrigerant chamber 86 collects on top of theliquid refrigerant in the pan 85 and passes to the left end of the panfrom which it flows through a suitable weir or port 88 in the end wall87 of the pan and into the sump 38. The chilled Water tube bundle 40 isspaced inwardly from the left end wall 87 to form a relatively quietarea 89 or liquid refrigerant upon which water in the pan collects.Thus, means is provided for separating water and refrigerant andreturning the separated fluids for reuse in the system.

When it is desired to provide only heating, as for winter heating, thecondensing water pump 42 is shut off and valve means 90 in the steamsupply line 20 to the turbocompressor 21 is adjusted so that the steambypasses the turbine 22 and is injected through a bypass line 91 intothe steam condenser 24 for heating the second condensing portion 55.During winter heating, the heating capacity of the system is preferablycontrolled by regulating the modulating fuel valve 16 in the fuel lineto the steam generator burner 13.

During winter heating operation, refrigerant may migrate into the steamcondenser 24, as from the refrigerant condenser 33 or through theturbine drain 31, and must be removed from the steam condenser alongwith any residual refrigerant therein in order to effect maximum heatingof the second tube bundle '55 which provides hot Water to the load to beheated. The noncondensible refrigerant vapor is withdrawn through thepurge line 53, and the water supply pump 50 is therefore in operation toprovide impeller water for the jet pump 52. In order to prevent waterfrom flashing at the jet pump 52, the impeller Water must be below thewater saturation temperature of the steam condenser 24, and moreparticularly, in the steam condensate chamber 64. Therefore, the waterline 51 to the jet pump 52 passes through a jet impeller water heatexchanger 92 for cooling the impeller water. A threeway valve 93 in thereturn branch 59 of the heating line 57 is adjusted to pass thereturning heating water through a line 94 to the heat exchanger 92, fromwhich the heating water returns through a line 95 to the return branch59 of the heating line 57 and then to the second condensing bundle. Theheat exchanger 92 assures a jet impeller water temperature at or veryclose to the temperature of the heating water entering the steamcondenser, and during winter heating operation the water saturationtemperature in the steam condensate chamber 64 is necessarily above thereturning heating water temperature. During simultaneous heating andcooling operation, the threeway valve 93 is adjusted so that thereturning heating water bypasses the heat exchanger 92 and flowsdirectly into the second condensing bundle 55.

Refrigerant storage means is provided to permit factory charging of thesystem with refrigerant, to store refrigerant during servicing of themachine, and for reducing the load on the purge system during winterheating operation at which time the refrigeration system is not inoperation. A refrigerant passage line 96 connects upper portions of aclosed refrigerant storage vessel 97 and the refrigerant chamber 86 ofthe cooler 36. When the turbocompressor 21 is inoperative, as duringwinter heating operation, the pressure in the refrigerant chamber 86 ismuch higher than during normal cooling operation. For example, duringnormal cooling operation the cooler may be at a pressure of about 5p.s.i.g., when the turbocompressor is stopped the pressure risesrapidly, and during heating operation the cooler may be at a pressure ofabout 50 p.s.i.g. The storage vessel 97 is maintained at a relativelylow temperature below the boiling point of the refrigerant so that therefrigerant vapor enters the storage vessel and condenses and remains inthe storage vessel. The walls 98 of the storage vessel 97 are exposed toambient air about the system so that under favorable conditions atemperature below the vapor point of the refrigerant is therebymaintained in the storage vessel. During winter heating operation, thesteam condenser 24 is at a substantially higher temperature than duringcooling operation, so that water in the cooler sump 38 is at a highertemperature, in part because the vapor injected through the purge systemis at a relatively high temperature. To assure proper condensing ofrefrigerant in the vessel 97, the blower 18, which may be on either sideof the vessel 97, is connected to pass combustion air through condensingmeans, here in the form of a tube bundle 99 within the storage vessel,thus assuring a relatively low temperature therein and preheating theair to the burner. It should be noted that the condensing bundle 99 inthe storage vessel is so positioned that when the charge of refrigerantis stored therein, a lower portion of the bundle is below the normalpredetermined level of liquid refrigerant and therefore immersed in theliquid refrigerant, and the upper portion of the bundle is exposed torefrigerant vapor for condensing the refrigerant vapor.

When the turbocompressor 21 is again operative, the pressure in thecooler 36 drops substantially, so that any refrigerant therein vaporizesand the reduced pressure in the line 96 to the storage vessel causes therefrigerant to boil out of the storage vessel and pass back into thecooler for circulation through the refrigerant side of the system. Theline 96 between the cooler refrigerant chamber 86 and the storage vessel97 is provided 'with a normally open shutoff valve 100, when closed forretaining the refrigerant in the storage vessel, as during servicing orshipping of the machine. Suitable pump-down connections may be provided.

The storage vessel 97 is positioned at an elevation above the cooler 36,and more particularly above the refrigerant pan 85, so that liquidrefrigerant and any water condensed in the storage vessel may be drainedtherefrom into the pan through a drain line 101. The drain line 101 hasa normally closed shutoff valve 102 for holding the liquids in thevessel. While this invention has been described and illustrated in apreferred embodiment, it will be understood that the invention is notlimited thereto since it may be otherwise embodied within the scope ofthe following claims.

I claim:

1. A heating and cooling system comprising, a cooler including a watersump and chilled means for cooling a load, a steam condenser including acondensing portion for condensing steam and heating a heating medium,

means for circulating the heating medium between said condensing portionand a load to be heated, steam driven operating means operable fordischarging steam into said steam condenser and for circulatingrefrigerant through said cooler for cooling the load during coolingoperation of the system, purge means responsive to circulating Waterthrough said sump at a temperature below that in said steam condenserfor removing noncondensibles from said steam condenser and including apurge line communicating with said steam condenser and a jet pumpoperated by the water and discharging said water and saidnoncondensibles into the cooler sump, storage means including a closedvessel and passage means connecting said cooler and said vessel for thepassage of refrigerant from said cooler into said vessel when saidoperating means is inoperative and for the passage of refrigerant fromsaid vessel into said cooler when operating means is in operation, meansfor bypassing steam around said operating means and into said steamcondenser to heat said heating medium and render said operatingtmeansinoperative during winter heating operation of the system, and heatexchange means in circuit during winter heating operation to associatesaid impeller water and the heating medium returning to said condensingportion and provide an impeller water temperature below the watersaturation temperature in said steam condenser, thereby effectivelypreventing flashing of water at the jet pump.

2. The system of claim 1 wherein said vessel is at an elevation above aportion of said cooler, drain means between a lower portion of saidvessel and said cooler for passing refrigerant liquid and any water insaid vessel to said cooler, valve means in said drain means for bold ingliquid in said vessel when the valve is closed, and means for separatingwater and refrigerant in said cooler and returning the separated fluidsfor reuse in the system.

3. The system of claim 1, and steam generator means for supplying steamto operate the system and including a burner, and air circulating meansfor circulating air to condense refrigerant vapor in the vessel and thenpassing the air to said burner, whereby the air passing to the bumer ispreheated as it cools the refrigerant in the vessel.

4. A heating and cooling system comprising, a cooler having a water sumpand chilled means for coolinga load, a steam condenser having acondensing portion for condensing steam and heating a heating medium forcircula tion between said condensing portion and a load to be heated,steam driven operating means operable for discharging steam into saidsteam condenser and for circulating refrigerant to said cooler andwithdrawing refrigerant from said cooler for cooling the chilled meansduring cooling operation of the system, means including a jet pump insaid sump and responsive to circulating impeller water from said sumpthrough said jet pump at a temperature below that in said steamcondenser, and a purge line be-,

tween said steam condenser and said jet pump for removingnoncondensibles from said steam condenser, means for bypassing steamaround said operating means and into said steam condenser to heat saidheating medium and render said operating means inoperative duringwinterheating operation of the system, and heat exchange means in circuitduring Winter heating operation for associating said impeller water andthe heating medium returning to said condensing portion to provide atemperature below that in the steam condenser, thereby effectively pre-.

venting flashing of the water in said jet pump.

References Cited by the Examiner UNITED STATES PATENTS 2,982,864 5/1961Furrebve 95 3,065,610 11/1962 Maudlin 62-149 3,153,442 10/1964 Silvern-50 ROBERT A. OLEARY, Primary Examiner. C. SUKALO, Assistant Examiner.

1. A HEATING AND COOLING SYSTEM COMPRISING, A COOLER INCLUDING A WATERSUMP AND CHILLED MEANS FOR COOLING A LOAD, A STEAM CONDENSER INCLUDING ACONDENSING PORTION FOR CONDENSING STEAM AND HEATING A HEATING MEDIUM,MEANS FOR CIRCULATING THE HEATING MEDIUM BETWEEN SAID CONDENSING PORTIONAND A LOAD TO BE HEATED, STEAM DRIVEN OPERATING MEANS OPERABLE FORDISCHARGING STEAM INTO SAID STEAM CONDENSER AND FOR CIRCULATINGREFRIGERANT THROUGH SAID COOLER FOR COOLING THE LOAD DURING COOLINGOPERATION OF THE SYSTEM, PURGE MEANS RESPONSIVE TO CIRCULATING WATERTHROUGH SAID SUMP AT A TEMPERATURE BELOW THAT IN SAID STEAM CONDENSERFOR REMOVING NONCONDENSIBLES FROM SAID STEAM CONDENSER AND INCLUDING APURGE LINE COMMUNICATING WITH SAID STREAM CONDENSER AND A JET PUMPOPERATED BY THE WATER AND DISCHARGING SAID WATER AND SAIDNONCONDENSIBLES INTO THE COOLER SUMP, STORAGE MEANS INCLUDING A CLOSEDVESSEL AND PASSAGE MEANS CONNECTING SAID COOLER AND SAID VESSEL FOR THEPASSAGE OF REFRIGERANT FROM SAID COOLER INTO SAID VESSEL WHEN SAIDOPERATING MEANS IS INOPERATIVE AND FOR THE PASSAGE OF REFRIGERANT FROMSAID VESSEL INTO SAID COOLER WHEN OPERATING MEANS IS IN OPERATION, MEANSFOR BYPASSING STEAM AROUND SAID OPERATING MEANS, AND INTO SAID STEAMCONDENSER TO HEAT SAID HEATING MEDIUM AND RENDER SAID OPERATING MEANSINOPERATIVE DURING WINTER HEATING OPERATION OF THE SYSTEM, AND HEATEXCHANGE MEANS IN CIRCUIT DURING WINTER HEATING OPERATION TO ASSOCIATESAID IMPELLER WATER AND THE HEATING MEDIUM RETURNING TO SAID CONDENSINGPORTION AND PROVIDE AN IMPELLER WATER TEMPERATURE BELOW THE WATERSATURATION TEMPERATURE IN SAID STEAM CONDENSER, THEREBY EFFECTIVELYPREVENTING FLASHING OF WATER AT THE JET PUMP.